Oral or nasal endotracheal intubation procedures are commonly employed to secure a controlled airway and to deliver inhalant oxygen, anesthetic gases, and other therapeutic agents into the trachea and lungs of human and veterinary patients. These clinical procedures are usually performed as a preliminary measure before surgery, thus enabling the anesthesiologist to administer anesthetic gases and other drugs while maintaining a stable delivery of oxygen to the patient's lungs throughout the surgical procedure. In other settings, intubation is used to provide a patient with a secure, direct airway when mechanical ventilation of the patient is indicated.
The conventional procedure for such intubation procedures involves the visualization of the glottis and adjacent anatomic areas with a laryngoscope. A laryngoscope typically includes a handle containing a power supply and an attached blade section that serves to displace the tongue and allow direct visualization of the patient's larynx through the mouth. The technique of orotracheal or direct nasotracheal intubation involves sighting the vocal cords and the insertion of an endotracheal tube therethrough in a patient who is usually anesthetized or unconscious. The laryngoscope blade is usually introduced laterally through the right side of the mouth, and then directed medially to exclude and retract the tongue for adequate visualization of the hypopharynx.
Training and experience combine to make intubation a safe, effective, and atraumatic technique. For example, a safe approach to intubation in advance of a surgical procedure involves first providing the patient with a short-acting sedative and a skeletal muscle relaxant before initiating laryngoscopy. Then, the head, neck, and shoulders of the patient must be positioned so that the oral, pharyngeal, and laryngeal axes are optimally aligned. Finally, the laryngoscope is inserted, preferably with the laryngoscopist's left hand—without regard to whether the laryngoscopist is right or left handed-laterally from the right side of the patient's mouth to avoid the incisor teeth and the tongue is deflected away from the lumen of the pharyngeal outlet by the tip of the laryngoscope blade. The epiglottis is sighted above the base of the tongue and, according to the type of laryngoscope blade used, the instrument is manipulated to expose the glottic opening. The endotracheal tube is then introduced through either the mouth or nose, and visually advanced between the vocal cords into the subglottic space. Once placement has been achieved, the laryngoscope blade is carefully removed to avoid either injury to oropharyngeal structures or unintentional displacement of the endotracheal tube.
Many types of laryngoscope blades have been developed, each characterized by blade curvature or lack thereof, the point of such curvature if the blade is curved, and the flange structure of the blade. Three types of blades are most prominently used. An example of a first type of blade, characterized as a curved blade, is known in the art as the MacIntosh blade. The MacIntosh blade is advanced into the space between the base of the tongue and the pharyngeal surface of the epiglottis. Forward and upward movement of this blade stretches the hypoepiglottic ligament to cause the epiglottis to move upward to expose the glottic opening. Two other types of prominently used blades are the straight blade, known as the Jackson or Wisconsin blade, and the straight blade with a curved tip, known in the art as the Miller blade. The tip of these blades are passed beneath the laryngeal surface of the epiglottis and moved upwardly to elevate the epiglottis, thereby exposing the glottic opening.
During insertion of the laryngoscope, care must be taken to avoid pressure on the teeth and gums of the patient. Care must also be taken to avoid traumatizing both the oral mucosa and the epiglottis. Use of a gentle technique for inserting the laryngoscope, may lessen, but cannot totally remove the possibility of intubation trauma. However, poor dentition or suboptimal anatomy of the teeth, jaw, neck, or throat may leave the maxillary incisors at particularly significant risk during intubation by even the most experienced of technicians.
When properly positioned, a laryngoscope blade may rest against the upper teeth of the maxilla, depending upon the individual patient's anatomy. Because the laryngoscope blade is necessarily formed of a hard, inflexible material, dental damage is a potential result of such intubation procedures. Such dental injury is typically aggravated when the upper teeth are used as a fulcrum during insertion procedures.
Even edentulous patients may be at risk for significant injuries to their maxillary alveolar ridges during the process of endotracheal intubation. The same mechanism of injury that may fracture or dislocate teeth may contuse or fracture the maxillary alveolar ridge, resulting in post-intubation difficulties in using the patient's previous dental prostheses or dentures. Such prostheses may have to be replaced, at considerable cost. In addition, residual local pain at the site of injury may aggravate the patient's tolerance for the use of any dental prostheses following such an intubation injury.
Various methods have been proposed to minimize such dental injury. Protected shields have limited advantage in preventing dental injuries during intubation. The shields cover the maxillary incisors, yet provide only limited protection for the teeth. Such shields are prone to displacement by either the laryngoscope blade or other instrumentation. Furthermore, existing shields are relatively difficult to use, requiring multiple operator steps to secure the shields for use. The multiple steps required to secure existing shields may discourage their use by significantly increasing the time and effort required to achieve the desired intubation. Moreover, the bulk of the protective shields may obstruct the user's view into the hypopharynx.
U.S. Pat. No. 3,826,248 to Gobels presents a laryngoscope blade in which an elastic insert which is anchored within a mating opening in the tongue deflector by means of undercut grooves extending in cross and longitudinal directions relative to each other.
U.S. Pat. No. 4,583,527 to Musicant et al. teaches the placement of an elongated layer of soft, pliable plastic material which is adhere to the upper surface of a sheath which is slidably and removably coupled to the flange or curved edge of the tongue deflector of a laryngoscope blade.
U.S. Pat. No. 5,065,738 to Van Dam provides for a flexible padded sheath, which is adhered along the length of a laryngoscope blade, covering substantially its entire outer surface.
U.S. Pat. No. 5,438,976 to Nash provides a self-adherent, deformable cushioning device wrapped around a laryngoscope blade along at least a portion of its length.
U.S. Pat. No. 5,776,053 to Dragisic et al. provides a laryngoscope blade with a cutout or recess in the vertical portion of the tongue deflector where a resilient insert is removably coupled at its proximal and distal ends.
The devices currently available do not satisfactorily address the need to protect a patient's teeth, as well as the needs of convenience and feasibility of use. Blade covers are cumbersome and slow to apply to the blade, and are therefore impractical in emergency situations. Moreover, a cushioning device should be easy to remove after use and should not leave a permanent residue on the blade or the patient's teeth or mouth. While blade covers currently available are generally used only once, a typical laryngoscope blade is reusable and is commonly sterilized in steam autoclaves between uses. Adhesives used in applying a blade cover to a blade often make it difficult to remove the blade cover and may leave a residue that is difficult to remove. Adhesive residues may become even more difficult to remove after the residue has been subjected to the heat and pressure of the sterilization process. In addition, any such residue on a reusable instrument may present a potential focus for infectious bacteria or other pathogenic organisms. Further, blade covers that surround the entire blade or entire flange occupy too much space in a patient's mouth, making manipulation of the laryngoscope blade and introduction of the endotracheal tube difficult.
Common user errors during positioning of a laryngoscope, as well as the particular structure of a given blade, may cause difficulties in proper introduction of an endotracheal tube. Such errors, which include the placement of the blade at an improper depth and incomplete displacement of the tongue, may be more likely with one blade over another. For example, complete displacement of the tongue may be more difficult with blades styles wherein the flange curves back over the blade, presenting a relatively small passageway for the actual passage of an endotracheal tube.